1. Heat the oil in a large saucepan over medium heat. Add the onions and 1/2 teaspoon salt and cook, stirring occasionally, until the onions are translucent, about 5 minutes. Add the garlic and cook, stirring, for 1 minute. Add the cumin, epazote, and chile and cook, stirring, for 1 minute.

2. Add the yuca, stock, tomatoes with their juices,and corn cobs. Bring to a boil, then reduce the heat and simmer until the yuca is tender, about 30 minutes. Add the corn kernels and cook just until heated through and still crisp-tender, about 3 minutes. Discard the corn cobs.

3. Using an immersion blender or stand blender (working in batches if necessary), puree about half of the soup until thickened. It should be creamy but still have bits of vegetables throughout. Stir the puree into the remaining soup. Serve with the crema, lime, avocado, and cilantro.